Implement raw DeviceMonitor

Multiple things have been done in this commit; the base of the new
backend has effectively been created. This branch currently has many
vital parts commented out. Therefore, this branch is currently only
intended for debugging.

src/logid/backend/hidpp/Device.cpp

@@ -0,0 +1,30 @@
+#include "Device.h"
+#include "Report.h"
+
+using namespace logid::backend;
+using namespace logid::backend::hidpp;
+
+const char* Device::InvalidDevice::what() const noexcept
+{
+    switch(_reason)
+    {
+        case NoHIDPPReport:
+            return "Invalid HID++ device";
+        case InvalidRawDevice:
+            return "Invalid raw device";
+    }
+}
+
+Device::InvalidDevice::Reason Device::InvalidDevice::code() const noexcept
+{
+    return _reason;
+}
+
+/// TODO: Initialize a single RawDevice for each path.
+Device::Device(std::string path, DeviceIndex index):
+    raw_device (std::make_shared<raw::RawDevice>(path)), path (path), index (index)
+{
+    supported_reports = getSupportedReports(raw_device->reportDescriptor());
+    if(!supported_reports)
+        throw InvalidDevice(InvalidDevice::NoHIDPPReport);
+}